TREK1000 with DecaRange + USB-to-SPI

I’m new to testing out the Decawave products and have a TREK1000 kit with 4 EVB1000 boards. The boards are currently running the default 2.10 software on the ARM cores. I can power on one anchor (A0), and one tag (T0), and have them report distance on the LCDs and the DecaRangeRTLS PC application.

I’d like to be able to read/write the DW1000 registers, while the DecaRangeRTLS ARM application is running, using the USB-to-SPI capability in the ARM application. From my PC virtual COM port, I see the range reports streaming out (starts with ‘mr’ or ‘mc’). When I try to send a command on my PC to the virtual COM port, I don’t see the SPI response string read back from the COM port, only the mr/mc ranges continuing. I do send the special 5 character ‘deca?’ init string as well from my PCs custom control application.

Any suggestions on what I might be doing wrong?